Invited Lecture: Prof. Dr. Eva Hemmer

Small yet bright?! Microwave-assisted synthesis of lanthanide-based nanoparticles

The remarkable optical properties of the lanthanides (Ln) make Ln-based materials ideal for
applications ranging from biomedicine to optoelectronics and energy conversion technology.
This is due the unique electronic properties of the Ln (f-elements) allowing for upconversion,
i.e., the emission of UV-visible light under near-infrared excitation. Upconverting nanoparticles
(UCNPs) based on sodium lanthanide fluorides (NaLnF4) are commonly synthesized by the
thermal decomposition of metal precursors in high-boiling-point solvents, based on
convectional heating. Microwave reactors can improve reproducibility as offering better control
over a reaction environment, more homogeneous heat distribution yields narrow size
distributions, and rapid heating to the desired temperature shortens reaction times from hours
to minutes. Targeting applications in optoelectronics, photochemistry, and energy conversion,
boosting the efficiency of upconverters is key. This presentation will shed light on the
microwave-assisted synthesis of core/(multi)shell UCNPs and highlight pros and cons of this
strategy towards the design of small-yet-bright upconverters.